Problem: Ashley is 6 years older than Gabriela. Six years ago, Ashley was 4 times as old as Gabriela. How old is Gabriela now?
Solution: We can use the given information to write down two equations that describe the ages of Ashley and Gabriela. Let Ashley's current age be $a$ and Gabriela's current age be $g$ The information in the first sentence can be expressed in the following equation: $a = g + 6$ Six years ago, Ashley was $a - 6$ years old, and Gabriela was $g - 6$ years old. The information in the second sentence can be expressed in the following equation: $a - 6 = 4(g - 6)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $g$ , it might be easiest to use our first equation for $a$ and substitute it into our second equation. Our first equation is: $a = g + 6$ . Substituting this into our second equation, we get the equation: $(g + 6)$ $-$ $6 = 4(g - 6)$ which combines the information about $g$ from both of our original equations. Simplifying both sides of this equation, we get: $g + 0 = 4 g - 24$ Solving for $g$ , we get: $3 g = 24$ $g = 8$.